Transliteration For Query Expansion

ABSTRACT

Methods, systems, and apparatus, including computer program products, for identifying candidate synonyms of transliterated terms for query expansion. In one aspect, a method includes identifying multiple transliterated terms in a target language. For each transliterated term of the multiple transliterated terms in the target language, the transliterated term is mapped to one or more terms in a source language. For a first transliterated term of the multiple transliterated terms in the target language, one or more second transliterated terms of the multiple transliterated terms in the target language are identified as candidate synonyms of the first transliterated term, where each of the one or more second transliterated terms is mapped to at least one term in the source language that is also mapped from the first transliterated term.

CROSS-REFERENCE TO RELATED APPLICATION

This Application is a continuation under 35 U.S.C. §120 of U.S. patentapplication Ser. No. 12/503,806, filed Jul. 15, 2009 and entitled“Transliteration for Query Expansion”, which claims the benefit under 35U.S.C. §119(e) of U.S. patent application Ser. No. 61/082,165, filedJul. 18, 2008. All of the aforementioned patent applications are herebyincorporated by reference in their entirety.

BACKGROUND

This specification relates to query expansion for users submittingqueries to search engines.

Search engines—and, in particular, Internet search engines—aim toidentify resources (e.g., web pages, images, text documents, multimediacontext) that are relevant to a user's needs and to present informationabout the resources in a manner that is most useful to the user.Internet search engines return search results in response to a usersubmitted query. If a user is dissatisfied with the search resultsreturned for a query, the user can attempt to refine the query to bettermatch the user's needs.

Some search engines provide a user with suggested alternative queries,for example, expanded queries, that the search engine identifies asbeing related to the user's query. Techniques for finding synonyms ofquery words for query expansion typically depend on natural languagemodels or user search log data. The identified synonyms of query wordscan be used to expand a query in an attempt to identify additional ormore relevant resources to improve user search experience.

Electronic documents are typically written in many different languages.Each language is normally expressed in a particular writing system(i.e., a script), which is usually characterized by a particularalphabet. For example, the English language is expressed using the Latinalphabet while the Hindi language is normally expressed using theDevanāgarī alphabet. The scripts used by some languages include aparticular alphabet that has been extended to include additional marksor characters. In transliteration, the script of one language is used torepresent words normally written in the script of another language. Forexample, a transliterated term can be a term that has been convertedfrom one script to another script or a phonetic representation in onescript of a term in another script. Techniques for finding synonyms ofquery words for query expansion may not work well for finding synonymsof query terms that are transliterated terms. For example, currentnatural language techniques do not work well with transliterated data,and search log data typically provide poor coverage for mosttransliterated variations.

SUMMARY

This specification describes technologies relating to identifyingcandidate synonyms of transliterated terms for query expansion.

In general, one aspect of the subject matter described in thisspecification can be embodied in computer-implemented methods thatinclude the actions of identifying, using one or more computers,multiple transliterated terms in a target language, for eachtransliterated term of the multiple transliterated terms in the targetlanguage, mapping the transliterated term to one or more terms in asource language, and for a first transliterated term of the multipletransliterated terms in the target language, identifying one or moresecond transliterated terms of the multiple transliterated terms in thetarget language as candidate synonyms of the first transliterated term,where each of the one or more second transliterated terms is mapped toat least one term in the source language that is also mapped from thefirst transliterated term. Other embodiments of this aspect includecorresponding systems, apparatus, and computer program products.

These and other embodiments can optionally include one or more of thefollowing features. Identifying the multiple transliterated terms in thetarget language can further include identifying from web resources termscontaining only characters of the target language. The aspect canfurther include computing a statistic for each identified termcontaining only characters of the target language, comparing thestatistic for each identified term to a specified threshold, andincluding a particular identified term in the multiple transliteratedterms in the target language if the statistic for the particularidentified term exceeds the specified threshold.

The statistic for each identified term can be a ratio of a probabilityof occurrence of the identified term in web resources of a top-leveldomain associated with one or more locales where the source language isspoken to a probability of occurrence of the identified term in webresources of a top-level domain associated with any locale. Thestatistic for each identified term can be a ratio of a probability ofoccurrence of the identified term in web resources associated with oneor more locales where the source language is spoken to a probability ofoccurrence of the identified term in web resources associated with anylocale. The association of a web resource with a locale where the sourcelanguage is spoken can be determined by a top-level domain of the webresource.

Mapping the transliterated term to one or more terms in the sourcelanguage can further include transliterating the transliterated term inthe target language to the one or more terms in the source language.Each of the one or more second transliterated terms identified ascandidate synonyms of the first transliterated term can have aconfidence value with respect to the first transliterated term that isabove a specified threshold. The confidence value of a secondtransliterated term can be a function of a number of terms in the sourcelanguage that are mapped from both the first transliterated term and thesecond transliterated term. Transliterating the transliterated term inthe target language to a term in the source language can further includegenerating a transliteration score for the transliteration of thetransliterated term in the target language to the term in the sourcelanguage. The confidence value of a second transliterated term can be afunction of one or more of a probability of occurrence of the secondtransliterated term in web resources, the transliteration score for thetransliteration of the second transliterated term to a term in thesource language that is also mapped from the first transliterated term,and the transliteration score for the transliteration of the firsttransliterated term to the term in the source language.

The aspect can further include, for the first transliterated term of themultiple transliterated terms in the target language, identifying one ormore terms in the source language that are mapped from the firsttransliterated term and from at least one of the one or more secondtransliterated terms as candidate synonyms of the first transliteratedterm. The aspect can further include receiving a query including thefirst transliterated term, expanding the query with one or more of thecandidate synonyms of the first transliterated term, providing theexpanded query to a search engine, and receiving search results for theexpanded query. The aspect can further include receiving a queryincluding the first transliterated term, and providing one or moreexpanded queries for selection by a user, each expanded query includingthe query and one or more of the candidate synonyms of the firsttransliterated term.

The aspect can further include receiving a query including the firsttransliterated term, providing the query to a search engine, where thesearch engine identifies as a possible search result for the query a webresource that includes at least one of the candidate synonyms of thefirst transliterated term but does not include any term in the query,and modifying a score associated with the web resource, the score foruse in ranking possible search results for the query. The aspect canfurther include receiving a query including the first transliteratedterm, providing the query to a search engine, where the search engineidentifies as a possible search result for the query a web resource thatincludes at least one of the terms in the source language that is mappedfrom the first transliterated term and from at least one of the one ormore second transliterated terms but does not include any term in thequery, and modifying an information retrieval score associated with theweb resource, the information retrieval score for use in rankingpossible search results for the query.

Another aspect of the subject matter described in this specification canbe embodied in computer-implemented methods that include the actions ofgenerating, using one or more computers, a training group of possibletransliterated synonyms in a target language, training a probabilisticmodel using the training group to learn probabilities of spellingvariations in transliterated synonyms in the target language, andapplying the probabilistic model to a particular transliterated term inthe target language to identify one or more candidate synonyms of theparticular transliterated term. Other embodiments of this aspect includecorresponding systems, apparatus, and computer program products.

Another aspect of the subject matter described in this specification canbe embodied in computer-implemented methods that include the actions ofidentifying, using one or more computers, multiple transliterated termsin a target language, for a first transliterated term of the multipletransliterated terms in the target language, identifying one or moresecond transliterated terms of the multiple transliterated terms in thetarget language as candidate synonyms of the first transliterated term,and using the candidate synonyms of the first transliterated term toexpand queries including the first transliterated term. Otherembodiments of this aspect include corresponding systems, apparatus, andcomputer program products.

Particular embodiments of the subject matter described in thisspecification can be implemented to realize one or more of the followingadvantages. Transliterated terms are identified as candidate synonymsfor a particular transliterated term, where the candidate synonyms canbe used for expanding queries including the particular transliteratedterm. Transliterated synonyms in a target language can be identified fornewer transliterated terms (e.g., terms transliterated from terms in asource language from current news stories or current culturalreferences), which may have poor coverage in user search log data. Asystem that can expand a user's query to include candidatetransliterated synonyms for a given transliterated term may returnbetter search results than a search system that does not have the samequery expansion capability.

The details of one or more embodiments of the subject matter describedin this specification are set forth in the accompanying drawings and thedescription below.

Other features, objects, and advantages of the subject matter will beapparent from the description, the drawings, and the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram of an example search system.

FIGS. 2A-2C illustrate an example technique for identifying candidatesynonyms for a transliterated term.

FIG. 3 is a flow chart of an example process for identifying candidatesynonyms for a transliterated term.

FIG. 4 is a flow chart of an example process for providing searchresults for an expanded query that includes a transliterated term and acandidate synonym.

FIG. 5 is a flow chart of an example process for identifying candidatesynonyms for a transliterated term.

Like reference symbols and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

FIG. 1 is a block diagram of an example search system 114 that can beused to provide search results relevant to submitted queries as can beimplemented in an Internet, an intranet, or another client and serverenvironment. The search system 114 is an example of an informationretrieval system in which the systems, components, and techniquesdescribed below can be implemented.

A user 102 can interact with the search system 114 through a clientdevice 104. For example, the client 104 can be a computer coupled to thesearch system 114 through a local area network (LAN) or wide areanetwork (WAN), e.g., the Internet. In some implementations, the searchsystem 114 and the client device 104 can be one machine. For example, auser can install a desktop search application on the client device 104.The client device 104 will generally include a random access memory(RAM) 106 and a processor 108.

A user 102 can submit a query 110 to a search engine 130 within a searchsystem 114. When the user 102 submits a query 110, the query 110 istransmitted through a network to the search system 114. The searchsystem 114 can be implemented as, for example, computer programs runningon one or more computers in one or more locations that are coupled toeach other through a network. The search system 114 includes an indexdatabase 122 and a search engine 130. The search system 114 responds tothe query 110 by generating search results 128, which are transmittedthrough the network to the client device 104 in a form that can bepresented to the user 102 (e.g., as a search results web page to bedisplayed in a web browser running on the client device 104).

When the query 110 is received by the search engine 130, the searchengine 130 identifies resources that match the query 110. The searchengine 130 will generally include an indexing engine 120 that indexesresources (e.g., web pages, images, or news articles on the Internet),an index database 122 that stores the index information, and a rankingengine 152 (or other software) that ranks the resources that match thequery 110. The search engine 130 can transmit the search results 128through the network to the client device 104 for presentation to theuser 102.

In some scenarios, a query includes one or more terms that aretransliterated terms. Transliteration converts a term in a sourcelanguage to a transliterated term in a target language. Afterconversion, the letters or characters of the term in the source languageare represented by letters or characters of the target language. Amachine learning technique for transliteration is described, forexample, in U.S. patent application Ser. No. 12/043,854, titled “MachineLearning for Transliteration,” filed Mar. 6, 2008.

Terms transliterated from one language to another language can be usedin Internet resources. For example, Indic languages like Hindi, Tamil,Telugu, Kannada, and Malayalam are sometimes transliterated to Englishon Internet resources (e.g., Indian blogs or electronic Indian technicaltextbooks). These languages, along with some non-Indic languages (e.g.,Chinese and other logographic writing systems) often do not havewell-developed alternate input mechanisms, such that it is cumbersome toenter characters in these languages.

Transliterations do not have a notion of correct spelling. As a result,there often exist multiple spellings in a target language fortransliterations of a word in a source language. For a particular termin a source language having multiple transliterations in a targetlanguage, transliterated terms in the target language that vary from agiven transliterated term in the target language can be treated ascandidate synonyms of the given transliterated term. These candidatetransliterated synonyms are different possible transliterations of thesame term in the source language.

As an example, the Hindi word,

, can be transliterated into English as “chakrabarti” or “chakrabarty”.Thus, the transliterated term “chakrabarty” can be identified as acandidate synonym of the given transliterated term, “chakrabarti”.

Candidate synonyms identified for a given transliterated term can beused to expand queries that include the given transliterated term. Forexample, if there is a popular new Hindi song available on severalwebsites on the Internet, a user may find it difficult to search for thesong if the websites transliterate a Hindi word in the song title to afirst transliterated term while the user enters a query with a secondtransliterated term for the same Hindi word. A search system that canexpand the user's query to include candidate transliterated synonyms forthe second transliterated term may return better search results than asearch system that does not have the same query expansion capability.

FIGS. 2A-2C illustrate an example technique for identifying candidatesynonyms for a transliterated term. For convenience, the exampletechnique will be described with reference to a system that performs thetechnique. The example technique can be used to expand a query includingthe transliterated term to include synonyms of the transliterated termin an attempt to improve the search results returned for the query. Theexample technique uses transliteration techniques to determine whatterms in a target language (e.g., English) are transliterated from thesame term in a source language (e.g., Hindi). Several techniques can beimplemented to increase the precision or quality of the candidatesynonyms.

FIG. 2A illustrates a list 210 of possible transliterated terms inEnglish, the target language, where the source language is Hindi. Asystem can generate or identify the list 210 of possible transliteratedterms in any number of different ways.

For example, the system can identify the possible transliterated termsof the list 210 from web resources as terms containing only charactersof the target language (e.g., Latin characters). The identified termscontaining only characters of the target language include words withmeaning in the target language and possible transliterated terms withoutmeaning in the target language.

To separate the possible transliterated terms from non-transliteratedterms (e.g., the words with meaning), the system can compute statisticsfor the identified terms containing only characters of the targetlanguage and can compare the statistics to a specified threshold. Thatis, for each identified term, a statistic is computed and compared to athreshold, where the system includes the identified term in the list 210of possible transliterated terms if the statistic for the identifiedterm exceeds the specified threshold.

In one example where English is the target language and Hindi is thesource language, transliterated terms in English may have a higherprobability of occurring on an Indian web resource than on non-Indianweb resources. In this example, the statistic for each identified termcontaining only Latin characters can be a function of the probability ofoccurrence on an Indian web resource.

In some implementations, the statistic for each identified term is aratio of the probability of occurrence of the identified term in webresources of a top-level domain associated with one or more locales(e.g., countries or regions) where the source language is spoken to theprobability of occurrence of the identified term in web resources of atop-level domain associated with any locale. For example, the statisticcould be the ratio of the probability of the identified term occurringon an Indian web page to the probability of the identified termoccurring on any web page. If the statistic computed for a particularidentified term exceeds a specified threshold, the particular identifiedterm can be included in the list 210 of possible transliterated terms.

In some other implementations, the statistic for each identified term isa ratio of the probability of occurrence of the identified term in webresources associated with one or more locales (e.g., countries orregions) where the source language is spoken to the probability ofoccurrence of the identified term in web resources associated with anylocale. The association of a web resource with a locale where the sourcelanguage is spoken can be determined by a top-level domain of the webresource. For example, the statistic could be the ratio of theprobability of the identified term occurring on an Indian web domain tothe probability of the identified term occurring on any web domain. Ifthe statistic computed for a particular identified term exceeds aspecified threshold, the particular identified term can be included inthe list 210 of possible transliterated terms.

In some scenarios, a particular web page or a particular web domain mayuse a particular identified term an exceptionally large number of times,which could skew the statistic for the particular identified term. Insome implementations, the system caps the statistic for each identifiedterm or a component of the statistic for each identified term at aspecified limit to prevent skewing of the statistic. For example, thesystem can cap the per-page contribution of the identified term onIndian web pages or the per-domain contribution of the identified termon Indian domains.

In some implementations, the statistic for each identified term is aratio of the probability of the identified term being included in aquery submitted to a search engine having an interface in the sourcelanguage to the probability of the identified term being included in aquery submitted to a search engine having an interface in any language.For the example, the system can compute the statistic using Indian andnon-Indian search logs.

In some implementations, to separate the possible transliterated termsfrom the non-transliterated terms (e.g., words with meaning in thetarget language), the system computes multiple statistics for eachidentified term containing only characters of the target language andcompares the multiple statistics to respective thresholds. If themultiple statistics for a particular identified term each exceed arespective threshold, the system can include the particular identifiedterm in the list 210 of possible transliterated terms.

The possible transliterated terms of the list 210 can alternatively beidentified by crawling only known web resources associated with thesource language. For the example where the source language is Hindi, thesystem can identify the possible transliterated terms by crawling knownIndian websites, for example, Indian blog sites or websites thattranslate Hindi songs or Hindi technical textbooks.

FIG. 2B illustrates relations 215 between each possible transliteratedterm of the list 210 and one or more terms 220 in the source language,Hindi. Each relation 215 is the result of mapping an element of a firstgroup (i.e., the possible transliterated terms in the target language)to one or more elements of a second group (i.e., the terms 220 in thesource language). That is, mapping forms a one-way relation between apossible transliterated term in the target language and one or moreterms 220 in the source language. In the example technique of FIG. 2B,the relations 215 are the result of mapping by transliterationperformed, for example, by an English-to-Hindi machine transliterator,implemented as an element of a system.

In some implementations, mapping includes generating a transliterationscore 225 for each transliteration from a possible transliterated termin the target language to a term 220 in the source language. Forexample, FIG. 2B illustrates the transliteration score 225 for eachtransliteration, including the score from “sreeram” to H2 (e.g.,score_(E1 to H2)), the score from “shriram” to H2 (e.g.,score_(E3 to H2)), and the score from “shreeram” to H6 (e.g.,score_(E4 to H6)).

If transliteration scores 225 are generated by mapping, thetransliteration score 225 of a given possible transliterated term of thelist 210 can be a component of a confidence value of the given possibletransliterated term with respect to another possible transliteratedterm. The system can use these confidence values in identifying thepossible transliterated terms that should be considered as candidatesynonyms for a particular transliterated term. The transliterationscores 225 and the confidence values are described in more detail withrespect to FIG. 2C.

FIG. 2C illustrates identifying, for a first possible transliteratedterm 230, one or more second possible transliterated terms 240 ascandidate synonyms of the first possible transliterated term 230.

If the transliterator maps a term 220 in the source language from two ormore possible transliterated terms in the target language, this suggestsa synonym relationship between the two or more possible transliteratedterms in the target language. For example, H2 is a Hindi word in thesource language that is mapped by the transliterator from three possibletransliterated terms: “sreeram”, “shriram”, and “shreeram”, suggestingthat the three transliterated terms are synonyms.

In the example technique of FIG. 2C, the system identifies the secondpossible transliterated terms 240 as candidate synonyms of the firstpossible transliterated term 230 by identifying the possibletransliterated terms of the list 210 that are mapped to at least oneterm 220 in the source language that is also mapped from the firstpossible transliterated term 230. Intersections of the terms 220 in thesource language give candidate groups for transliterated synonyms.Several techniques can be implemented to increase the reliability of thecandidate groups for transliterated synonyms. In some implementations,each of the possible transliterated terms of the list 210 other than thefirst possible transliterated term 230 has a confidence value withrespect to the first possible transliterated term 230. In theseimplementations, if a particular possible transliterated term has aconfidence value with respect to the first possible transliterated term230 that is above a specified threshold, the particular possibletransliterated term is a second possible transliterated term 240identified as a candidate synonym of the first possible transliteratedterm 230. If mapping does not produce a transliteration score 225 foreach transliteration, the confidence value for a given second possibletransliterated term 240 can be a function of the number of terms 220 inthe source language that are mapped from both the first possibletransliterated term 230 and the given second possible transliteratedterm 240.

For example, “shriram” and “sriraam” each map to only one term 220(i.e., H2 and H6, respectively) that is also mapped from “sreeram”, thefirst possible transliterated term 230. The transliterated term“shreeram” maps to two terms 220 (i.e., H2 and H6) that are also mappedfrom “sreeram”, the first possible transliterated term 230. The overlapwith “sreeram” of mapped terms 220 in the source language is greater for“shreeram” than for “shriram” and “sriraam”, suggesting that “shreeram”might be a more reliable candidate synonym for “sreeram” than either“shriram” or “sriraam”. This increased reliability can be reflected in ahigher confidence value for “shreeram” with respect to “sreeram”.

If mapping produces a transliteration score 225 for eachtransliteration, the confidence value for a given second possibletransliterated term 240 can be a function of the transliteration scores225 of the first possible transliterated term 230 and of the givensecond possible transliterated term 240. For example, the confidencevalue for “shriram”, a second possible transliterated term 240, withrespect to “sreeram”, the first possible transliterated term 230, whereboth transliterated terms map to H2, can be a function of thetransliteration scores 225 score_(E1 to H2) and score_(E3 to H2).

In some implementations, the confidence value for a given secondpossible transliterated term 240 is a function of a probability ofoccurrence of the given second possible transliterated term 240 in webresources. For example, the probability of occurrence can be theper-page contribution in web resources or the per-domain contribution inweb resources of the given second possible transliterated term 240.Generally, a higher probability of occurrence suggests that the givensecond possible transliterated term 240 is a more common form of thetransliteration from the term in the source language. A higherprobability suggests higher confidence in the common transliteratedterm, which can be reflected in a higher confidence value for thetransliterated term.

In some implementations, the confidence value for a given secondpossible transliterated term 240 is a function of multiple components,e.g., the transliteration scores 225 and a probability of occurrence.Although FIG. 2C includes as second possible transliterated terms 240all possible transliterated terms that map to a term 220 in the sourcelanguage that are also mapped from the first possible transliteratedterm 230, implementation of any of the above techniques for increasingthe reliability of candidate groups can reduce the group of candidatesynonyms to a subgroup of the second possible transliterated terms 240illustrated in FIG. 2C.

In some implementations, the system identifies one or more of the terms220 in the source language that are mapped from the first possibletransliterated term 230 and from at least one of the second possibletransliterated terms 240 as candidate synonyms of the first possibletransliterated term 230 in addition to or instead of the second possibletransliterated terms 240. For example, for the first possibletransliterated term 230, “sreeram”, the system can identify the terms H2and H6 as candidate synonyms of “sreeram”. In some implementations, thesystem identifies the terms 220 in the source language that are mappedfrom the same transliterated term in the target language as a candidatesynonym group. For the example of FIG. 2C, the system can identify theterms H2 and H6, mapped from the same transliterated terms “sreeram” and“shreeram”, as a candidate synonym group.

The system can use the candidate transliterated synonyms (i.e., thesecond possible transliterated terms 240) for query expansion. Forexample, when a search system (e.g., the search system 114 of FIG. 1)receives a query including the first possible transliterated term 230,the search system can identify one or more candidate transliteratedsynonyms of the first possible transliterated term 230. The query can beexpanded with one or more of the identified candidate transliteratedsynonyms of the first possible transliterated term 230. In the exampleof FIG. 2C, the system can expand a query including “sreeram” to includeone or more of “shriram”, “shreeram’, and “sriraam”. In someimplementations, the system ranks the candidate synonyms by confidencevalue, and the system selects only N candidate synonyms with the Nhighest confidence values for including in expanded queries. The systemprovides the expanded query to a search engine (e.g., the search engine130 of FIG. 1), and receives search results for the expanded query.

In some implementations, if the system selects a possible transliteratedterm as a candidate transliterated synonym for a given transliteratedterm, the system also selects the given transliterated term as acandidate transliterated synonym for the possible transliterated term.In other implementations, if the system selects a possibletransliterated term as a candidate transliterated synonym for a giventransliterated term, the system does not select the given transliteratedterm as a candidate transliterated synonym for the possibletransliterated term. That is, there may or may not be reverse mapping oftransliterated synonyms. For example, if a first transliterated term “a”is rarely used and a second transliterated term “b” is often used, queryexpansion of “a” with “b” generally makes sense, because the expansionwill result in more search results returned. However, automaticallyexpanding queries of “b” with “a” may not make sense, because theexpansion may return irrelevant search results.

In some implementations, instead of expanding a query with one or morecandidate transliterated synonyms, mapping candidate transliteratedsynonyms to a given transliterated term occurs on the document side of aquery search. For the above example, if a user submits a query includingthe transliterated term “b” but not the transliterated term “a” and if aweb document contains “a” but not “b,” the search system (e.g., thesearch system 114 of FIG. 1) can treat the web document as if the webdocument also contains “b,” so that the web document is a candidatesearch result for the search including “b.” However, since the webdocument does not actually include “b,” the search system can reduce ascore associated with the web document (e.g., an information retrievalscore for ranking the web document as a candidate search result), which,consequently, can reduce the chance of the web document being returnedfor the search.

In some implementations, document-level mapping of candidate synonymsincludes one or more terms 220 in the source language. For the exampleof FIG. 2C, the search system can treat a web document containing“sreeram” as if the web document also contains the Hindi word H2 or H6.The search system can also reduce a score associated with the webdocument accordingly.

FIG. 3 is a flow chart of an example process 300 for identifyingcandidate synonyms for a transliterated term. For convenience, theexample process 300 will be described with reference to the exampletechnique of FIGS. 2A-2C and a system that performs the process 300.

The system identifies multiple transliterated terms in a target language(step 310). For example, the system identifies the possibletransliterated terms of the list 210 in FIG. 2A.

For each transliterated term of the multiple transliterated terms in thetarget language, the system maps the transliterated term to one or moreterms in a source language (step 320). FIG. 2B illustrates an example ofmapping using an English-to-Hindi transliterator.

For a first transliterated term of the multiple transliterated terms inthe target language, the system identifies one or more secondtransliterated terms of the multiple transliterated terms as candidatesynonyms of the first transliterated term (step 330). Each of the one ormore second transliterated terms is mapped to at least one term in thesource language that is also mapped from the first transliterated term.For example, FIG. 2C illustrates second possible transliterated terms240 (i.e., “shriram”, “shreeram”, and “sriraam”) identified as candidatesynonyms of a first possible transliterated term 230 (i.e., “sreeram”).The candidate synonyms can be used for query expansion, for example, asdescribed with respect to FIG. 4.

FIG. 4 is a flow chart of an example process 400 for providing searchresults for an expanded query that includes a transliterated term and acandidate synonym. For convenience, the example process 400 will bedescribed with reference to the example technique of FIG. 2A-2C and asystem that performs the process 400.

The system receives a query including a first transliterated term (step410). For example, the query can include the transliterated term“sreeram” illustrated in FIG. 2C.

The system provides one or more expanded queries for selection by auser, where each expanded query includes the query and one or morecandidate synonyms of the first transliterated term (step 420). Thecandidate synonyms can be identified, for example, using the exampleprocess 300 of FIG. 3. For a query including the transliterated term“sreeram”, the system can provide expanded queries that also include oneor more of “shriram”, “shreeram”, and “sriraam”, as illustrated in FIG.2C.

The system receives a selection of an expanded query from the user (step430). For example, the expanded queries can be presented to the user asselectable hyperlinks on an interface of a web browser running on aclient device (e.g., the client device 104 of FIG. 1). The system canreceive the selection of an expanded query as a selection by the user ofthe hyperlink for the selected expanded query. In some implementations,the system generates an expanded query with one or more of the candidatesynonyms and proceeds to step 440 without performing steps 420 and 430.The system provides the expanded query to a search engine (step 440).For example, the system can submit the expanded query to the searchengine 130 of FIG. 1. The search engine performs the search, sendingsearch results for the expanded query to the system. The system receivesthe search results for the expanded query (step 450).

In some implementations, the system provides the received query of step410 to the search engine without expanding the query. Instead, thesystem performs document-level mapping as described above with respectto FIG. 2C. For example, the search engine can identify as a possiblesearch result for the query a web resource that includes at least one ofthe candidate synonyms of the first transliterated term but does notinclude any term (e.g., the first transliterated term) in the query.Alternatively, the search engine can identify as a possible searchresult for the query a web resource that does not include any term(e.g., the first transliterated term) in the query but that does includeat least one of the terms in a source language that is mapped from thefirst transliterated term and from at least one of the candidatesynonyms. When document-level mapping is implemented, the system canmodify (e.g., reduce) a score for use in ranking that is associated withthe web resource identified as a possible search result.

FIG. 5 is a flow chart of an example process 500 for identifyingcandidate synonyms for a transliterated term. For convenience, theexample process 500 will be described with reference to a system thatperforms the process 500. In general, the process 500 directly learnspossible variations in spelling for transliterated terms in a targetlanguage. Since transliterated synonyms are generally phoneticallysimilar, the variations between the transliterated synonyms are languagespecific.

The system generates a training group of possible transliteratedsynonyms in a target language (step 510). The system trains aprobabilistic model using the training group to learn probabilities ofspelling variations in transliterated synonyms in the target language(step 520). The system applies the probabilistic model to a particulartransliterated term in the target language to identify one or morecandidate synonyms of the particular transliterated term (step 530). Thesystem can use the candidate synonyms for query expansion as describedabove.

Embodiments of the subject matter and the functional operationsdescribed in this specification can be implemented in digital electroniccircuitry, or in computer software, firmware, or hardware, including thestructures disclosed in this specification and their structuralequivalents, or in combinations of one or more of them. Embodiments ofthe subject matter described in this specification can be implemented asone or more computer program products, i.e., one or more modules ofcomputer program instructions encoded on a tangible program carrier forexecution by, or to control the operation of, data processing apparatus.The tangible program carrier can be a propagated signal or acomputer-readable medium. The propagated signal is an artificiallygenerated signal, e.g., a machine-generated electrical, optical, orelectromagnetic signal, that is generated to encode information fortransmission to suitable receiver apparatus for execution by a computer.The computer-readable medium can be a machine-readable storage device, amachine-readable storage substrate, a memory device, a composition ofmatter effecting a machine-readable propagated signal, or a combinationof one or more of them.

The term “data processing apparatus” encompasses all apparatus, devices,and machines for processing data, including by way of example aprogrammable processor, a computer, or multiple processors or computers.The apparatus can include, in addition to hardware, code that creates anexecution environment for the computer program in question, e.g., codethat constitutes processor firmware, a protocol stack, a databasemanagement system, an operating system, or a combination of one or moreof them.

A computer program (also known as a program, software, softwareapplication, script, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, or declarative orprocedural languages, and it can be deployed in any form, including as astand-alone program or as a module, component, subroutine, or other unitsuitable for use in a computing environment. A computer program does notnecessarily correspond to a file in a file system. A program can bestored in a portion of a file that holds other programs or data (e.g.,one or more scripts stored in a markup language document), in a singlefile dedicated to the program in question, or in multiple coordinatedfiles (e.g., files that store one or more modules, sub-programs, orportions of code). A computer program can be deployed to be executed onone computer or on multiple computers that are located at one site ordistributed across multiple sites and interconnected by a communicationnetwork.

The processes and logic flows described in this specification can beperformed by one or more programmable processors executing one or morecomputer programs to perform functions by operating on input data andgenerating output. The processes and logic flows can also be performedby, and apparatus can also be implemented as, special purpose logiccircuitry, e.g., an FPGA (field programmable gate array) or an ASIC(application-specific integrated circuit).

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, andany one or more processors of any kind of digital computer. Generally, aprocessor will receive instructions and data from a read-only memory ora random access memory or both. The essential elements of a computer area processor for performing instructions and one or more memory devicesfor storing instructions and data. Generally, a computer will alsoinclude, or be operatively coupled to receive data from or transfer datato, or both, one or more mass storage devices for storing data, e.g.,magnetic, magneto-optical disks, or optical disks. However, a computerneed not have such devices. Moreover, a computer can be embedded inanother device, e.g., a mobile telephone, a personal digital assistant(PDA), a mobile audio or video player, a game console, a GlobalPositioning System (GPS) receiver, a device with spoken language input,to name just a few. A smart phone is an example of a device with spokenlanguage input, which can accept voice input (e.g., a user query spokeninto a microphone on the device).

Computer-readable media suitable for storing computer programinstructions and data include all forms of non-volatile memory, mediaand memory devices, including by way of example semiconductor memorydevices, e.g., EPROM, EEPROM, and flash memory devices; magnetic disks,e.g., internal hard disks or removable disks; magneto-optical disks; andCD-ROM and DVD-ROM disks. The processor and the memory can besupplemented by, or incorporated in, special purpose logic circuitry.

To provide for interaction with a user, embodiments of the subjectmatter described in this specification can be implemented on a computerhaving a display device, e.g., a CRT (cathode ray tube) or LCD (liquidcrystal display) monitor, for displaying information to the user and akeyboard and a pointing device, e.g., a mouse or a trackball, by whichthe user can provide input to the computer. Other kinds of devices canbe used to provide for interaction with a user as well; for example,feedback provided to the user can be any form of sensory feedback, e.g.,visual feedback, auditory feedback, or tactile feedback; and input fromthe user can be received in any form, including acoustic, speech, ortactile input.

Embodiments of the subject matter described in this specification can beimplemented in a computing system that includes a back-end component,e.g., as a data server, or that includes a middleware component, e.g.,an application server, or that includes a front-end component, e.g., aclient computer having a graphical user interface or a Web browserthrough which a user can interact with an implementation of the subjectmatter described is this specification, or any combination of one ormore such back-end, middleware, or front-end components. The componentsof the system can be interconnected by any form or medium of digitaldata communication, e.g., a communication network. Examples ofcommunication networks include a local area network (“LAN”) and a widearea network (“WAN”), e.g., the Internet.

The computing system can include clients and servers. A client andserver are generally remote from each other and typically interactthrough a communication network. The relationship of client and serverarises by virtue of computer programs running on the respectivecomputers and having a client-server relationship to each other.

While this specification contains many specific implementation details,these should not be construed as limitations on the scope of anyinvention or of what may be claimed, but rather as descriptions offeatures that may be specific to particular embodiments of particularinventions. Certain features that are described in this specification inthe context of separate embodiments can also be implemented incombination in a single embodiment. Conversely, various features thatare described in the context of a single embodiment can also beimplemented in multiple embodiments separately or in any suitablesubcombination. Moreover, although features may be described above asacting in certain combinations and even initially claimed as such, oneor more features from a claimed combination can in some cases be excisedfrom the combination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. In certain circumstances, multitasking and parallel processingmay be advantageous. Moreover, the separation of various systemcomponents in the embodiments described above should not be understoodas requiring such separation in all embodiments, and it should beunderstood that the described program components and systems cangenerally be integrated together in a single software product orpackaged into multiple software products.

Particular embodiments of the subject matter described in thisspecification have been described. Other embodiments are within thescope of the following claims. For example, the actions recited in theclaims can be performed in a different order and still achieve desirableresults. As one example, the processes depicted in the accompanyingfigures do not necessarily require the particular order shown, orsequential order, to achieve desirable results. In certainimplementations, multitasking and parallel processing may beadvantageous.

What is claimed is:
 1. A computer-implemented method comprising:identifying, using one or more computers, a plurality of transliteratedterms in a target language, each of the transliterated termsrepresenting a conversion in the target language of one or morerespective source terms in a source language; for each transliteratedterm of the plurality of transliterated terms in the target language,mapping the transliterated term to one or more of the source terms inthe source language; determining that a first transliterated term of thetransliterated terms is mapped to one or more terms of the source termsin the source language and that one or more second transliterated termsof the transliterated terms are also mapped to the one or more terms;and identifying, based on the one or more terms being mapped to thefirst transliterated term and being mapped to the one or more secondtransliterated terms, the one or more second transliterated terms ascandidate synonyms of the first transliterated term.
 2. The method ofclaim 1, where mapping the transliterated term to one or more sourceterms in the source language further comprises: transliterating thetransliterated term in the target language to the one or more sourceterms in the source language.
 3. The method of claim 2, where each ofthe one or more second transliterated terms identified as candidatesynonyms of the first transliterated term has a confidence value withrespect to the first transliterated term that satisfies a specifiedthreshold.
 4. The method of claim 3, where the confidence value of asecond transliterated term of the one or more second transliteratedterms is a function of a number of the one or more terms in the sourcelanguage that are mapped from both the first transliterated term and thesecond transliterated term.
 5. The method of claim 3, wheretransliterating the transliterated term in the target language to theone or more source terms in the source language further comprises:generating a transliteration score for each transliteration of thetransliterated term in the target language to a respective source termof the one or more source terms.
 6. The method of claim 5, where theconfidence value of a second transliterated term of the one or moresecond transliterated terms is a function of one or more of aprobability of occurrence of the second transliterated term in webresources, the transliteration scores for the transliteration of thesecond transliterated term to the one or more same terms that are alsomapped from the first transliterated term, and the transliterationscores for the transliteration of the first transliterated term to theone or more same terms.
 7. The method of claim 1, where identifying theplurality of transliterated terms in the target language furthercomprises: identifying terms containing only characters of the targetlanguage.
 8. The method of claim 7, further comprising: computing astatistic for each identified term containing only characters of thetarget language; comparing the statistic for each said identified termto a specified threshold; and including a particular said identifiedterm in the plurality of transliterated terms in the target language ifthe statistic for the particular identified term satisfies the specifiedthreshold.
 9. The method of claim 1, further comprising: for the firsttransliterated term of the plurality of transliterated terms in thetarget language, identifying the one or more same terms in the sourcelanguage that are mapped from the first transliterated term and from theone or more second transliterated terms as a candidate synonym of thefirst transliterated term.
 10. The method of claim 1, furthercomprising: receiving a query including the first transliterated term;expanding the query with one or more of the candidate synonyms of thefirst transliterated term; providing the expanded query to a searchengine; and receiving search results for the expanded query.
 11. Themethod of claim 1, further comprising: receiving a query including thefirst transliterated term; and providing one or more expanded queriesfor selection by a user, each expanded query including the query and oneor more of the candidate synonyms of the first transliterated term. 12.The method of claim 1, further comprising: receiving a query includingthe first transliterated term; providing the query to a search engine,where the search engine identifies as a possible search result for thequery a web resource that includes at least one of the candidatesynonyms of the first transliterated term but does not include any termin the query; and modifying a score associated with the web resource,the score for use in ranking possible search results for the query. 13.The method of claim 1, further comprising: receiving a query includingthe first transliterated term; providing the query to a search engine,where the search engine identifies as a possible search result for thequery a web resource that includes at least one of the terms in thesource language that is mapped from the first transliterated term andfrom the one or more second transliterated terms but does not includeany term in the query; and modifying an information retrieval scoreassociated with the web resource, the information retrieval score foruse in ranking possible search results for the query.
 14. A systemcomprising: one or more computers configured to perform operationsincluding: identifying, using one or more computers, a plurality oftransliterated terms in a target language, each of the transliteratedterms representing a conversion in the target language of one or morerespective source terms in a source language; for each transliteratedterm of the plurality of transliterated terms in the target language,mapping the transliterated term to one or more of the source terms inthe source language; determining that a first transliterated term of thetransliterated terms is mapped to one or more terms of the source termsin the source language and that one or more second transliterated termsof the transliterated terms are also mapped to the one or more terms;and identifying, based on the one or more terms being mapped to thefirst transliterated term and being mapped to the one or more secondtransliterated terms, the one or more second transliterated terms ascandidate synonyms of the first transliterated term.
 15. The system ofclaim 14, where mapping the transliterated term to one or more sourceterms in the source language further comprises: transliterating thetransliterated term in the target language to the one or more sourceterms in the source language.
 16. The system of claim 15, where each ofthe one or more second transliterated terms identified as candidatesynonyms of the first transliterated term has a confidence value withrespect to the first transliterated term that satisfies a specifiedthreshold.
 17. The system of claim 16, where the confidence value of asecond transliterated term of the one or more second transliteratedterms is a function of a number of the one or more terms in the sourcelanguage that are mapped from both the first transliterated term and thesecond transliterated term.
 18. The system of claim 16, wheretransliterating the transliterated term in the target language to theone or more source terms in the source language further comprises:generating a transliteration score for each transliteration of thetransliterated term in the target language to a respective source termof the one or more source terms.
 19. The system of claim 18, where theconfidence value of a second transliterated term of the one or moresecond transliterated terms is a function of one or more of aprobability of occurrence of the second transliterated term in webresources, the transliteration scores for the transliteration of thesecond transliterated term to the one or more same terms that are alsomapped from the first transliterated term, and the transliterationscores for the transliteration of the first transliterated term to theone or more same terms.
 20. The system of claim 14, where identifyingthe plurality of transliterated terms in the target language furthercomprises: identifying terms containing only characters of the targetlanguage.
 21. The system of claim 20, where the one or more computersare further configured to perform operations including: computing astatistic for each identified term containing only characters of thetarget language; comparing the statistic for each said identified termto a specified threshold; and including a particular said identifiedterm in the plurality of transliterated terms in the target language ifthe statistic for the particular identified term satisfies the specifiedthreshold.
 22. The system of claim 14, where the one or more computersare further configured to perform operations including: for the firsttransliterated term of the plurality of transliterated terms in thetarget language, identifying the one or more same terms in the sourcelanguage that are mapped from the first transliterated term and from theone or more second transliterated terms as a candidate synonym of thefirst transliterated term.